Overview

Serum liver chemistry tests, commonly called liver tests, or (mistakenly) liver function tests, are ordered for many reasons. Most laboratories offer these tests as a bundle, and this usually includes:

Bilirubin (breakdown product of the RBC after conjugation in the liver and secretion in biliary system excretion)

Individual tests in these panels are not specific for liver disease. Therefore, pattern recognition is critical. Isolated elevation of liver tests is a less common occurrence in liver diseases, and a nonhepatic source should also be considered in such instances. Evaluation of patients with abnormal liver tests should be guided by history, risk for liver disease, duration and severity of clinical findings, presence of comorbidities, and the nature of the liver test abnormality noted.

Traditionally, liver tests abnormalities have been grouped under the following patterns:

Bilirubin may be elevated in any category of liver disease, and this does not aid in the classification. [2] Isolated gamma-GT elevations are so common and so often unhelpful that many institutions have chosen to delete this test from their liver test panel. [3] When other liver tests are abnormal, categorization according to the pattern found is clinically valuable in the process of finding the possible etiology of the liver disease. However, liver tests can be abnormally elevated in 1% to 4% of the asymptomatic population, and further investigations reveal that 6% of these patients have no obvious cause for liver disease (liver histology may be normal). [4][5] In addition, people with liver disease may have normal tests (16% of patients with hepatitis C and 13% of patients with varying histologic damage due to nonalcoholic fatty liver diseases have persistently normal tests). [6] Liver tests may also be normal in people with hepatitis B who are in the immune-tolerant phase and in the inactive HBsAg carrier state. [7][8]